Hydrosols including microbubbles and related methods

ABSTRACT

Hydrosols including microbubbles and related methods are described. The microbubbles can increase the reflectivity of the water, thus, brightening the water. Consequently, light which would otherwise be absorbed by the water may be reflected. This limits the increase in water temperature which would otherwise result from such light absorption.

RELATED APPLICATIONS

This application claims priority to U.S. patent application Ser. No. 61/211,869, entitled “Hydrosols and Albedo”, by Seitz, filed on Apr. 3, 2009, which is incorporated herein by reference in its entirety.

FIELD OF INVENTION

The invention relates generally to hydrosols and, more particularly, to hydrosols including microbubbles distributed in water. The microbubbles may increase the reflectivity and albedo of the water and decrease light absorption.

BACKGROUND OF INVENTION

Water covers a large portion of the Earth's surface and is regularly exposed to sunlight. A high percentage of sunlight incident upon water is absorbed. Such absorption can raise the temperature of water.

A number of disadvantages may result from heating water including evaporation which depletes water supply. Also, higher temperatures limit the ability of water to function as a cooling source, for example, in industrial applications which use water to dissipate heat. Accordingly, technologies that mitigate increases to water temperature resulting from exposure to light may be desirable.

SUMMARY OF INVENTION

Hydrosols including microbubbles and related methods are described.

In one aspect, a hydrosol is provided. The hydrosol comprises microbubbles distributed in water. A majority of the microbubbles have a diameter of less than 20 microns. The hydrosol has a mass of greater than 100 tons.

In one aspect, a hydrosol is provided. The hydrosol comprises microbubbles distributed in water. A majority of the microbubbles have diameter of less than 10 micron. The concentration of microbubbles in the hydrosol is less than 10 ppm and greater than 0.1 ppm.

In one aspect a method is provided. The method comprises providing a hydrosol including microbubbles distributed in water. A majority of the microbubbles have an average diameter of less than 20 micron. The hydrosol has a mass of greater than 100 tons.

Other aspects, embodiments and features of the invention will become apparent from the following detailed description when considered in conjunction with the accompanying drawings. The accompanying figures are schematic and are not intended to be drawn to scale. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the invention shown where illustration is not necessary to allow those of ordinary skill in the art to understand the invention. All patent applications and patents incorporated herein by reference are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a schematic of a hydrosol including microbubbles.

FIG. 2 is a graph which models the reflectivity and albedo gain for a hydrosol according to one embodiment.

DETAILED DESCRIPTION

Hydrosols including microbubbles and related methods are described. In some embodiments, the hydrosols are formed by introducing the microbubbles into water. The microbubbles may, for example, have an average diameter of less than about 20 microns. The water phase of the hydrosol may have a large volume, mass and/or surface area. As described further below, the microbubbles can increase the reflectivity and albedo of the water. Thus, light which would otherwise be absorbed by the water may be reflected and the water surface may be brightened. This limits the increase in water temperature which would otherwise result from such light absorption. Consequently, the resulting hydrosol has a reduced temperatures as compared to water without the microbubbles. Reducing the temperature of water may have a number of advantages which may depend, in part, on the particular application in which the technology is used. For example, lower temperatures can help conserve water by reducing evaporation. Also, thermal transfer to water having lower temperature may be enhanced due to the thermodynamic considerations. Thus, hydrosols including microbubbles may be a more efficient cooling source which can lead to performance advantages, for example, in applications in which water is used for cooling purposes (e.g., cooling ponds for power plants).

FIG. 1 schematically illustrates a hydrosol 10 according to an embodiment. Hydrosol 10 includes a plurality of microbubbles 12 which are distributed in water 14. In general, microbubbles are tiny gas filled voids in the water, as described further below.

Microbubbles 12 are characterized by having a small diameter. In some embodiments, a majority (i.e., greater than 50%) of the microbubbles have a diameter of less than 20 microns; in some embodiments, a majority of the microbubbles have a diameter of less than 10 microns; and, in some embodiments, a majority of the microbubbles have an average diameter of less than 5 microns. In some cases, the majority of the microbubbles have a diameter of greater than 0.1 micron. In some cases, a preferred microbubble diameter is on the order of two times greater than the wavelength of visible light being reflected.

In some embodiments, at least 75%, or at least 95%, or substantially all, of the microbubbles have the above-described diameters.

A suitable technique for determining the diameter involves examining a representative number of microbubbles, for example using a suitable analytical technique (e.g., using a flow cytometer), to determine their size. It should also be understood that the size of a given microbubble may change over time as a result of various changes in conditions and other factors. For example, a microbubble may shrink over time. Owing to their small buoyancy, microbubbles rise in water at very low velocities, and may remain suspended in Brownian motion for up to hours or days without reaching the water surface, as described further below, if the vertical convection velocity of the water exceeds the rate of microbubble rise dictated by Stokes Law.

The microbubbles generally have a spherical shape as a result of surface energy considerations, though it is possible that small deviations from spherical shape may be possible under certain conditions.

The microbubbles may be formed by any suitable gas. In some embodiments, it is preferable that the microbubbles are formed by air. However, in other embodiments, other gases (e.g., argon) may be suitable.

The microbubbles may be distributed in the water in a variety of ways. In the illustrative embodiment, the microbubbles are generally distributed evenly throughout the volume of the water. In other embodiments, the concentration of microbubbles may be greater in certain regions of the water than in other regions of the water. For example, some hydrosols may include microbubble rich regions and microbubble poor regions. In particular, embodiments that include one or more point source(s) of microbubble formation, as described further below, may result in the variation of microbubble concentration within the hydrosol. In some embodiments, the microbubble rich region may be localized at or near the surface of the hydrosol. For example, the microbubble rich region may extend from the surface to a depth of about 10 meters or less; in some embodiments, to a depth of about 1 meter or less; and, in some embodiments, to a depth of about 25 cm or less. It should also be understood that the distribution of microbubbles throughout a body of water may change over time.

The concentration of microbubbles in the hydrosol may depend in part on the application in which the hydrosol is used. In some embodiments, it may be preferable for the concentration of microbubbles to be relatively dilute. Dilute hydrosols may be able to achieve desirable reflectivity properties, while facilitating the process of producing the hydrosol. For example, the concentration of microbubbles in the hydrosol may be less than 100 ppm by volume. In some cases, the concentration may be less than 10 ppm by volume; and, in some cases, less than 1 ppm by volume. In some embodiments, it is advantageous for the concentration to be greater than a minimum value to enhance the reflectivity of the resulting hydrosol. For example, the concentration may be greater than 0.01 ppm by volume; or, in some cases, greater than 0.1 ppm by volume. It should be understood that these minimum values may be found in combination with any of the maximum values noted above in certain embodiments.

It also should be understood that the above-noted microbubble concentration values may pertain to the entire hydrosol. That is, the concentration(s) may be calculated based on the entire volume of the hydrosol. In some case, the above-noted concentration values may pertain to a portion of the hydrosol. That is, the concentration(s) may pertain to a portion of the volume of the entire hydrosol. The portion may be, for example, a microbubble rich near surface region of the hydrosol, as described above. The portion may occupy, for example, less than or equal to 2.5%, less than or equal to 25%, less than or equal to 50% or less than or equal to 95% of the total volume of the hydrosol.

As noted above, the hydrosol generally has a large volume, mass and/or surface area. Such characteristics are generally desirable for many of the applications of the hydrosols. For example, the hydrosol may have a weight of greater than 100 tons. In some embodiments, the volume may be significantly higher including greater than 1,000 tons; greater than 10,000 tons; greater than 100,000 tons; and greater than 100,000,000 tons or significantly higher. In some embodiments, the hydrosol may have a volume of at least 100 m³; in some cases, at least 1000 m³; in some cases, at least 10,000 m³; in some cases, at least 100,000 m³; and, in some cases, at least 1,000,0000 m³ or significantly higher The surface area of the hydrosol (e.g., the area of the hydrosol exposed to light) may be greater than 100 m²; in some cases, greater than 10,000 m²; and, in some cases, greater than 1 km², greater than 10 km², or significantly higher It should be understood that the large volume, mass and/or surface area is almost entirely due to the water phase as the microbubble phase have relatively small volumes, mass and/or surface areas. It should also be understood that some embodiments include hydrosols having volume, mass and/or surface areas outside the above-noted ranges.

The type of water phase in the hydrosol may depend in part on the application in which the hydrosol is used. In some cases, the water may be used as a cooling source or heat sink for solar and/or thermal energy. The cooling source may be associated with a heat-producing source (such as a power plant), for example, in an industrial application. The water may be a man-made source; or, in some embodiments, the water may be natural source. The water may be a portion, or an entire, pond, lake, sea, river, or ocean. The water phase of the hydrosol may include other components. The other components may change certain properties of the water, for example, to enhance desirable characteristics. In some cases, the components change the viscosity and/or surface tension of the water in a manner that enhances microbubble presence and/or formation.

The components may be naturally present in the body of water. Example of suitable natural components include plant or animal life, or residues therefrom (e.g., phytoplankton lipids, fish oil, etc); as well as, inanimate components such as colloidal or nanoparticles derived from weathering or partial dissolution of rocks, sand, etc.

In some cases, the components may be added to the body of water. Examples of suitable components added to the body of water include surfactants (e.g., sodium lauryl sulfate, sodium alginate, carrageen, cetyl alcohol, lethicins, etc). The components may be dissolved within the water, or may be in solid form. When in solid form, the component(s) may be in the form of a colloid; or, may otherwise be distributed in the water.

As noted above, the hydrosols described herein generally have a higher reflectivity and albedo as compared to water without microbubbles. It should be understood that yhe term “albedo” refers to the ratio of the total reflected to total incident electromagnetic radiation. It can be determined by measuring the amount of light reflected from the hydrosol and comparing it to the amount of light incident on the hydrosol. The amount of light may be measured using known detection techniques including techniques that use a photodetector. In some embodiments, the albedo of the hydrosol is at least 1.1 times greater than the albedo of water without the microbubbles; in some embodiments; in some embodiments, the albedo of the hydrosol is at least 1.5 times greater than the albedo of water without the microbubbles; in some embodiments, the albedo of the hydrosol is at least 2 times greater than the albedo of water without the microbubbles; in some embodiments, the albedo of the hydrosol is at least 3 times greater than the albedo of water without the microbubbles; and, in some embodiments, the albedo of the hydrosol is at least 4 times greater than the albedo of water without the microbubbles. The degree of increase of reflectivity and albedo depends on a variety of factors including microbubble diameter and concentration. The desired reflectivity and albedo also will depend on the application in which the hydrosol is used.

As a result of the increase in reflectivity, the hydrosol absorbs less light which would otherwise increase the temperature of water. Thus, the presence of the microbubbles mitigates the increase in temperature. Consequently, the temperature of the hydrosol including the microbubbles is reduced compared to the temperature of the water in the absence of microbubbles, and by sinking of the cooler water, reduced temperatures may be imparted to the region beneath that in which the hydrosol bubbles are distributed. The degree of temperature reduction depends on a variety of factors including the degree of change in reflectivity (which as noted above also depends on a variety of factors including microbubble diameter and concentration) and the volume of the hydrosol, amongst other factors. In some embodiments, the change in temperature may be at least 1° C.; in some embodiments, at least 2° C.; in some embodiments, at least 5° C.; and, in some embodiments, at least 10° C.

FIG. 2 is a graph which models the reflectivity and albedo gain for a hydrosol according to one embodiment. In this model, the microbubbles are assumed to be 1 micron in diameter. The graph shows the reflectivity gain and albedo increase as a function of microbubble concentration in volume parts per million. The graph also shows maximum cooling in ° C.

It has been discovered that the hydrosols can be relatively stable over long periods of time. For example, the hydrosols can exhibit useful reflectivity over long periods of time. The stability may arise in part from the fact that the microbubbles in natural waters may have long lifetimes relative to the theortical rate of bubble disappearance in purified (e.g. distilled) microparticle free water. The specific lifetime depends on the size of the microbubble and the viscosity of the fluid, the presence of a surfactant and/or detergent in the fluid, amongst other factors. However, the microbubbles described herein may have lifetimes of greater than several hours or more. For example, a majority (i.e., greater than 50%) of the microbubbles have a lifetime of greater than 1 hour; and, in some cases, greater than 2 hours. The relative stability of the hydrosols can be a significant advantage in maintaining performance over time.

In general, the hydrosols can be made using any suitable technique. Such techniques generally involve generating microbubbles of gas in water. Certain suitable techniques involve generating microbubbles by supersaturating water with air (e.g., at elevated pressures) followed by rapidly reducing the pressure (e.g., by injection) to nucleate air bubbles within the water as a result of a decrease in air solubility in the water. Certain suitable techniques uses a vortex nozzle to generate the microbubbles which are injected into water. For example, the technique may use a vortex microbubble generator system.

In some embodiments, microbubbles are introduced into water at one or more locations. In some embodiments, a highly concentrated hydrosol is produced which is introduced into a larger body of water at on or more locations. In both cases, the number of locations depends in part on the desired microbubble concentration and the desired volume and mass of the hydrosol, amongst other factors such as the natural dispersion of fluids by flow from their point of entry into a body of water. One of skill in the art would be able to select suitable processing parameters depending on the desired hydrosol characteristics.

In techniques that use large bodies of water, suitable techniques for introducing large number of microbubbles may be used. For example, if the hydrosol is formed in a portion of the ocean or lake, ship engines or air compressors carried on ships for purposes of hull drag reduction may be used to power sources of microbubble formation, as well as to move the craft from which they are dispersed.

In some embodiments, the energy used for microbubble and hydrosol formation may be obtained from environmentally-friendly sources such as solar energy or wind energy.

As noted above, the hydrosols reflect more light than water without the presence of microbubbles. Thus, the surface of the water is brightened. This limits the increase in water temperature which would otherwise result from light and solar energy absorption. This can lead to a number of advantages including reducing evaporation which can help conserve water. Numerous examples of water conservation can be achieved including increased river flow, extended dry season water supply, increased lake area and conserved wetlands, amongst many others. Also, due to their lower temperature, the hydrosols may also function as more efficient cooling sources. This can translate into significant performance advantages in applications in which water is used for cooling purposes (e.g., in industrial applications). For example, the performance of cooling sources (also referred to as cooling ponds) for power plants may be significantly enhanced by using hydrosols including microbubbles instead of water without microbubbles.

Another benefit associated with hydrosols is that the above-noted advantages can be achieved on scales large enough to alter the global climate without disadvantages associated with other techniques including stratospheric aerosol techniques (which have disadvantages of lack of control and reversibility), chemical contamination, reduction in atmospheric CO₂, ozone layer risk, methane release, amongst others. The above-described brightening effect may be achieved without adding pigment (e.g., titanium dioxide) to the water which would be cost prohibitive to achieve the same brightening effect. Hydrosols may also be applied to reducing water temperatures in coastal or lakeside regions in order to conserve energy by reducing air conditioning power demand, to reducing or reversing environmental degradation arising from thermal stress due to high water temperatures, to reducing urban temperatures and air conditioning demand by extending efforts to brighten roofs and roads to urban and suburban waters, to generating tax offset revenue on land and at sea by providing increases in water albedo that offset radiative forcing of climate by CO₂ emissions. The hydrosols described herein may also be applied to change the color of water inexpensively for ornamental and/or aesthetic purposes, for example, in swimming pools, water park designs, as well as landscaping, riparian or costal seascape architecture.

Having thus described several aspects of at least one embodiment of the technology, it is to be appreciated that various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be within the spirit and scope of the technology. Accordingly, the foregoing description and drawings provide non-limiting examples only. 

1. A hydrosol comprising: microbubbles distributed in water, wherein a majority of the microbubbles have a diameter of less than 20 microns, wherein the hydrosol has a mass of greater than 100 tons.
 2. The hydrosol of claim 1, wherein a majority of the microbubbles have a diameter of less than 10 microns.
 3. The hydrosol of claim 1, wherein the concentration of microbubbles in the hydrosol is less than 10 ppm.
 4. The hydrosol of claim 3, wherein the concentration of microbubbles in the hydrosol is greater than 0.1 ppm
 5. The hydrosol of claim 1, wherein the hydrosol has a mass of greater than 1000 tons.
 6. The hydrosol of claim 1, wherein the hydrosol is a cooling source.
 7. The hydrosol of claim 6, wherein the hydrosol is a cooling pond of a power plant.
 8. The hydrosol of claim 1, wherein the reflectivity of the hydrosol has a reflectivity at least 5% greater than the reflectivity of the water in the absence of microbubbles.
 9. The hydrosol of claim 1, wherein the hydrosol has a surface area of at least 100 m².
 10. The hydrosol of claim 1, wherein a majority of the microbubbles have a lifetime of greater than 1 hour.
 11. The hydrosol of claim 1, wherein at least 75% of the microbubbles have a diameter of less than 20 microns.
 12. A hydrosol comprising: microbubbles distributed in water, wherein a majority of the microbubbles have diameter of less than 10 micron, wherein the concentration of microbubbles in the hydrosol is less than 10 ppm and greater than 0.1 ppm.
 13. A method comprising: providing a hydrosol including microbubbles distributed in water, wherein a majority of the microbubbles have an average diameter of less than 20 micron, wherein the hydrosol has a mass of greater than 100 tons.
 14. The method of claim 13, further comprising exposing the hydrosol to light.
 15. The method of claim 13, further comprising using the hydrosol as a cooling source.
 16. The method of claim 13, further comprising using the hydrosol as a cooling source for a power plant.
 17. The method of claim 13, wherein providing the hydrosol comprises supersaturating water with air to form a supersaturated solution and reducing the pressure of the supersaturated solution to produce the microbubbles.
 18. The method of claim 13, wherein the concentration of microbubbles in the hydrosol is less than 10 ppm and greater than 0.1 ppm. 